This research project will seek to develop radioimmunoassays (RIA) and enzyme-linked immunoabsorbent assays (ELISA) which will allow precise quantitation of serum antibodies against antigens from Candida albicans. The investigator has labeled with 125I the major immunogen of Candida, the cell wall mannan. This reagent will be used to develop sensitive, precise radioimmunoassays to measure antimannan antibody levels in sera. The mannan will be linked to a suitable enzyme and an ELISA will be developed to measure antimannan antibody. Methods to detect free mannan and mannan-antibody complexes in sera will be developed. Cytoplasmic extracts from Candida will be fractionated into component antigens. RIA or ELISA will be developed with each of these antigens to measure specific antibody. The application of all these immunoassays to diagnosing severe candidiasis in humans will be studied. The antimannan antibody response will be studied in mice infected with Candida. Models will be developed to study mannan antigenemia and the antimannan antibody response that occurs when Candida disseminates from various portals of entry. Experiments will be done to determine the cell populations involved in regulation of the antimannan responses. The intent will be to elucidate fundamental mechanisms that might be responsible for the control of the antibody response against any antigen.